Fuel cell technology has become a viable option for the automotive industry to generate power for vehicle operation. Certain types of fuel cells, such as proton exchange fuel cells (PEM fuel cells), generate electricity by delivering a flow of hydrogen gas to the anode side of a membrane-electrode-assembly and a flow of oxygen gas to the cathode side. A proton-conducting electrolyte sandwiched between the anode and cathode facilitates proton transport from the anode to the cathode while forcing electrons generated at the anode to move through an external circuit to reach the cathode. This external flow of electric current can be harnessed to drive an electric motor or other power-consuming device within the automobile. Many similar individual fuel cells may be stacked in series flow arrangement to produce a greater power supply, if necessary.
The hydrogen needed to operate a hydrogen-consuming fuel cell that helps power a vehicle is generally stored in an on-board storage device at pressures between 10 bar and 875 bar and at temperatures between −80° C. and 85° C. The fuel cell generally requires, however, a low and constant-pressure hydrogen supply that ranges from about 6 bar to about 12 bar at a load-dependent flow rate. To address this issue, flow control hydrogen pressure regulators, solenoid valves, and other devices that include dynamic and static seals may be incorporated into the vehicle's hydrogen storage and supply systems. These seals have to perform under constraints that are somewhat specific to hydrogen gas and fuel cell operation. For example, the use of lubricants at seal surface interfaces is quite limited because commonly-used lubricants tend to poison the fuel cell catalyst materials found in the anode and cathode and thus contribute to fuel cell performance degradation. As another example, the seals must be able to remain impermeable and withstand the low temperatures—down to around −80° C.—that result when hydrogen gas expands to meet the delivery pressure requirements of the fuel cell. The seal mating surfaces should also be as smooth as possible to avoid the formation of microscopic interstices through which the very small hydrogen gas molecules can escape.
Elastomer seals of a relatively low Young's modulus in conjunction with a heating mechanism have been used in the past for hydrogen storage and supply systems. The heating mechanism is needed because the higher flexibility elastomer seals become brittle and thus pervious to hydrogen gas as the hydrogen approaches its lower operating temperatures. Seals with a higher Young's modulus, and thus more rigidity, can perform adequately without a heating mechanism but are less able to tightly conform to the surface topography of the seal mating surface, and are more easily eroded when subjected to relative frictional movement against an adjacent non-lubricated surface. Hydrogen leakage and complications in hydrogen pressure management due to unreliable seal performance is thus a recurring issue for fuel cell hydrogen storage and supply systems. Better seal performance is therefore needed.